1. Field of the Invention
The invention relates to a stripping arrangement for preventing liquid from penetrating at the peripheral gap between a reciprocating component and a casing opening surrounding the latter, in particular an oil scraper packing for the piston rod of a piston compressor, with a stripping bushing formed around the component in the area of the casing opening for holding at least one stripping ring, which exhibits a drain for removing the stripped liquid.
2. The Prior Art
To prevent working, coolant or lubricant fluids from penetrating at the seal in reciprocating, sealed components, e.g., the mentioned piston rod of a piston compressor, steaming machines, hydraulic pumps or presses or the like, packings with special stripping rings are most often used today in addition to other seals to strip the liquid from the moved component and return or separately remove it. To always be able to remain in stripping contact with the surface of the moved component, these stripping rings must have some clearance in the stripping bushing in the direction of movement of the component, so that they can follow the surface of the component to be stripped, and hence, for example, varying heat expansions cannot impede the relative motion of the stripping rings one to another or to the stripping bushing as the result of jamming, which would lead to larger leaks and the undesired penetration of liquid to be stripped.
In previously known arrangements of the mentioned type, especially on the inlet side of the stripping bushing facing the area with the liquid to be stripped, this always results in a relatively large amount of liquid entering in a radial direction between the first stripping ring and the inside of the stripping bushing. Difficulties are often encountered in removing this liquid as fast as possible from the packing area lying to be back due to lines that are most often small in design, and therefore become clogged easily. As a result, the most often present additional stripping rings or similar elements have major problems with the liquid that then not only adheres to the reciprocating component, but is present in the entire packing area.
The object of this invention is to improve an arrangement of the kind mentioned at the outset in such a way as to avoid the mentioned disadvantages to known arrangements like these, and to prevent excessive liquid entry in the stripping bushing, in particular in a structurally simple manner.
This object is achieved according to the present invention in a stripping arrangement of the kind mentioned above by providing a choke ring in the stripping bushing on the side facing the inlet of the liquid to be stripped, which has a smooth annular surface on its front side facing the inlet of the liquid, and adheres to the smooth inner front surface of the stripping bushing facing it during operation, due to the adhesive forces in the liquid.
This limits the possible entry of liquid into the stripping bushing to the remaining annular gap between the moved component and choke ring. This annular gap can on the one hand normally be clearly smaller, and hence designed less problematically in terms of its impact on possible liquid entry than the gap which is necessary for the movement of the stripping rings, as mentioned, and is always present on the inlet side in an axial direction, at least during the xe2x80x9cinwardxe2x80x9d movement of the component to be stripped in conventional arrangements such as these. On the other hand, this annular gap is far less critical, since the amount of liquid still passing through it essentially adheres to the reciprocating component anyway, and is therefore stripped away by the downstream stripping ring and then removed as described. Hence, of the two remaining paths on the inlet side of the stripping bushing for the liquid to be stripped from the reciprocating component, the more critical path that allows larger amounts of liquid through between the front side of the first ring of the packing and the inner front side of the stripping bushing stays easily and reliably blocked.
The necessary snug fit of the choke ring to the accompanying inner front side of the stripping bushing during the xe2x80x9coutwardxe2x80x9d movement of the reciprocating component (out of the stripping bushing) is ensured by the reciprocating component or the stripping rings arranged on it anyway. In the other direction, the adhesive force in the liquid in the gap between the inner front side of the stripping bushing and accompanying front surface of the choke ring must be large enough to ensure that this inlet path is not opened for the liquid to be stripped for the short duration of this movement.
In a preferred further development of the invention, the choke ring is divided, preferably diagonally divided in two, and is held together after built in by a spring-loaded element mounted on its outside periphery. Its internal diameter is slightly larger than the outside diameter of the reciprocating component. This permits an easy assembly of the choke ring, wherein the mentioned diameter ratios ensure that the reciprocating component can practically freely move through the choke ring. In particular, the liquid to be removed is not stripped from the reciprocating component. As described above, this is accomplished by the downstream stripping rings.
At this point, it must be noted that the reciprocating component can also exhibit a design that deviates from the pure circular cylindrical shape that is largely common in such drive rods and the like. In particular, sliding rods or the like designed with an oval or other cross section can naturally be equipped with the described stripping arrangement, provided only the xe2x80x9cstripping ringsxe2x80x9d or xe2x80x9cchoke ringsxe2x80x9d exhibit an appropriately adjusted internal contour.
In an especially preferred further development of the invention, the choke ring is made out of plastic, preferably fiber-reinforced plastic, such as PTFE (polytetrafluorethylene) reinforced with glass fiber or carbon fiber. These types of rings are easy to manufacture, and chemically very stable, which makes them suitable for most applications in question.
In another preferred embodiment of the invention, the annular surface between the front surfaces of the stripping bushing and choke ring is considerably, advantageously about ten times, larger than the front-side contacting surface of the stripping ring(s). In this way, the large application surface enables a good sealing of this possible entry way for the liquid to be stripped into the stripping bushing on the one hand, and the adhesive force in the liquid on the other side, namely between the choke ring and downstream stripping ring, also remains significantly smaller than the adhesive force essential to the invention between the choke ring and accompanying front side of the stripping bushing. As a result, the choke ring remains fixed relative to the stripping bushing during the inwardly directed stroke of the component to be stripped, while the downstream stripping ring can move along with the component to a slight extent using the axial clearance in the stripping bushing.
In another preferred embodiment of the invention, the or each stripping ring arranged on the side of the choke ring in the stripping bushing facing away from the entry of the liquid to be stripped is divided, preferably diagonally divided in two, held together after built in by a spring-loaded element mounted on its outside periphery, and consists of a metal material, preferably bronze for bearings and bushes. As a result, the stripping effect of this stripping ring downstream from the choke ring in the direction of the inlet for the liquid to be stripped can be improved or simplified in terms of installation. The bronze for bearings and bushes enables close mounting on the reciprocating component, without excessively high friction and the problems associated therewith.
Particularly advantageous in the above connection is a further development of the invention, in which the radial thickness of the stripping ring is as small as possible taking into account strength and manufacturing requirements, preferably about 4 mm. As a result, the stripping ring can still adapt well to the surface of the reciprocating component, which is especially advantageous when this component exhibits deviations from the ideal, e.g., circular cylindrical shape or already has the corresponding worn areas. This small radial thickness also makes it possible to keep the force of the spring-loaded element mounted on the outside periphery at a relatively low level. In turn, this reduces the friction losses addressed above and associated areas that have become heated, expanded and the like.
In another especially preferred embodiment of the invention, the side of the stripping ring facing the inlet of the liquid to be stripped exhibits a stripping edge that is in contact with the reciprocating component when built in, and proceeding from that a slight conical area on the inside periphery that opens toward the other side. On the one hand, the closest possible, snug fit of the stripping ring is concentrated on a stripping edge that loops in relatively easily as a result. On the other hand, this enables the return of liquid (liquid film) that still manages to penetrate under the stripping edge during stripping due to surface roughness of the reciprocating component. As a result, the liquid is not stripped on the opposing other side of the stripping ring, and hence transported in an undesired manner to remain permanently behind the stripping arrangement.
In another preferred embodiment of the invention, the choke ring and stripping ring exhibit essentially radially aligned draining grooves on their front side facing away from the inlet of the liquid to be stripped. As a result, the stripped liquid can flow away between these elements largely unimpeded without having to provide separate spacing elements or the like.
In another preferred embodiment of the invention, at least one gas seal ring set and/or another choke ring that interacts with the inner front surface of the stripping bushing facing away from the inlet of the liquid to be stripped can be arranged in the stripping bushing, on the side of the stripping ring(s) facing away from the choke ring. This results in another improvement of the stripping effect also on the external side of the stripping bushing relative to the inlet of the liquid to be stripped.
In the following, the invention will be described in even greater detail based upon the embodiments schematically depicted in the drawings.